Tracing resistance to the antimalarial drug sulfadoxine across Africa

[Sally Furniss]

Multiple Origins and Regional Dispersal of Resistant dhps in African Plasmodium falciparum Malaria


Richard J. Pearce¹, Hirva Pota¹, Marie-Solange B. Evehe², El-Hadj Bâ³, Ghyslain Mombo-Ngoma⁴^,⁵, Allen L. Malisa⁶^,⁷, Rosalynn Ord¹, Walter Inojosa⁸, Alexandre Matondo⁹, Diadier A. Diallo¹⁰, Wilfred Mbacham², Ingrid V. van den Broek¹¹, Todd D. Swarthout¹¹, Asefaw Getachew¹², Seyoum Dejene¹³, Martin P. Grobusch⁴^,¹⁴, Fanta Njie¹⁵, Samuel Dunyo¹⁵^†, Margaret Kweku¹, Seth Owusu-Agyei¹^,¹⁶, Daniel Chandramohan¹, Maryline Bonnet¹⁷, Jean-Paul Guthmann¹⁷^,¹⁸, Sian Clarke¹, Karen I. Barnes¹⁹, Elizabeth Streat²⁰, Stark T. Katokele²¹, Petrina Uusiku²¹, Chris O. Agboghoroma²², Olufunmilayo Y. Elegba²², Badara Cissé²³, Ishraga E. A-Elbasit²⁴, Hayder A. Giha²⁴^,²⁵, S. Patrick Kachur²⁶, Caroline Lynch¹, John B. Rwakimari²⁷, Pascalina Chanda²⁸, Moonga Hawela²⁸, Brian Sharp²⁹^†, Inbarani Naidoo²⁹, Cally Roper¹^*
1 London School of Hygiene & Tropical Medicine, Department of Infectious Tropical Diseases, London, United Kingdom, 2 Biotechnology Centre, University of Yaounde I, Cameroon, 3 Institut de Recherche pour le Développement, Dakar, Senegal, 4 Medical Research Unit, Albert Schweitzer Hospital, Lambaréné, Gabon, 5 Department of Parasitology, Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany, 6 Ifakara Health Research and Development Center (IHRDC), Ifakara, Kilombero District, Tanzania, 7 Sokoine University of Agriculture, Department of Biological Sciences, Faculty of Science, Morogoro, Tanzania, 8 Doctors with Africa CUAMM Angola, Luanda, Angola, 9 Director of Uige Provincial Hospital, Uige Angola, 10 Centre National de Recherche et de Formation Sur Le Paludisme (CNRFP), Ouagadougou, Burkina Faso, 11 Médecins Sans Frontières, Manson Unit, London, United Kingdom, 12 Head of Malaria Department, Tigray Bureau of Health, Tigray, Ethiopia, 13 Médecins Sans Frontières – Ethiopia, Addis Ababa, Ethiopia, 14 Infectious Diseases Unit Division of Clinical Microbiology and Infectious Diseases, National Health Laboratory Service and School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa, 15 Medical Research Council Laboratories, The Gambia, 16 Kintampo Health Research Centre, Ghana, 17 Epicentre, Paris, France, 18 Institut de Veille Sanitaire, Paris, France, 19 Division of Clinical Pharmacology, Department of Medicine, University of Cape Town, Cape Town, South Africa, 20 Ministry of Health, Matola, Maputo Province, Mozambique, 21 National Malaria Control Programme, Ministry of Health and Social Services, Old State Hospital Grounds, Windhoek, Namibia, 22 National Hospital Abuja, Garki Abuja, Nigeria, 23 Université Cheikh Anta Diop de Dakar, Dakar, Senegal, 24 Malaria Research Centre, Department of Biochemistry, University of Khartoum, Khartoum, Sudan, 25 Department of Biochemistry, Faculty of Medicine and Medical Sciences, Arabian Gulf University, Manama, Kingdom of Bahrain, 26 Malaria Branch, Division of Parasitic Diseases, National Center for Zoonotic, Vector-Borne and Enteric Diseases, Centers for Disease Control and Prevention (CDC), Atlanta, Georgia, United States of America, 27 Ministry of Health of Uganda, National Malaria Control Programme, Kampala, Uganda, 28 National Malaria Control Centre, Lusaka, Zambia, 29 Malaria Research Lead Programme, Medical Research Council, Durban, South Africa
Abstract Top

Background

Although the molecular basis of resistance to a number of common antimalarial drugs is well known, a geographic description of the emergence and dispersal of resistance mutations across Africa has not been attempted. To that end we have characterised the evolutionary origins of antifolate resistance mutations in the dihydropteroate synthase (dhps) gene and mapped their contemporary distribution.
Methods and Findings

We used microsatellite polymorphism flanking the dhps gene to determine which resistance alleles shared common ancestry and found five major lineages each of which had a unique geographical distribution. The extent to which allelic lineages were shared among 20 African Plasmodium falciparum populations revealed five major geographical groupings. Resistance lineages were common to all sites within these regions. The most marked differentiation was between east and west African P. falciparum, in which resistance alleles were not only of different ancestry but also carried different resistance mutations.
Conclusions

Resistant dhps has emerged independently in multiple sites in Africa during the past 10–20 years. Our data show the molecular basis of resistance differs between east and west Africa, which is likely to translate into differing antifolate sensitivity. We have also demonstrated that the dispersal patterns of resistance lineages give unique insights into recent parasite migration patterns.
Citation: Pearce RJ, Pota H, Evehe M-SB, Bâ E-H, Mombo-Ngoma G, et al. (2009) Multiple Origins and Regional Dispersal of Resistant dhps in African Plasmodium falciparum Malaria. PLoS Med 6(4): e1000055. doi:10.1371/journal.pmed.1000055
Editor: Lorenz von Seidlein, Joint Malaria Project, United Republic of Tanzania
Received: May 30, 2008; Accepted: February 13, 2009; Published: April 14, 2009
Copyright: © 2009 Pearce et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The study was funded by the Gates Malaria Partnership (GMP). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Abbreviations: CQ, chloroquine; CQR, chloroquine resistance; IPTi, Intermittent Preventive Treatment of Malaria in Infants; IPTp, Intermittent Preventive Treatment of Malaria in Pregnancy; SP, sulphadoxine–pyrimethamine
* E-mail: Cally.Roper@lshtm.ac.uk
^† Deceased.

Editors' Summary Top

Background

Plasmodium falciparum, a mosquito-borne parasite that causes malaria, kills nearly one million people every year, mostly in sub-Saharan Africa. People become infected with P. falciparum when they are bitten by a mosquito that has acquired the parasite in a blood meal taken from an infected person. P. falciparum malaria, which is characterized by recurring fevers and chills, anemia (loss of red blood cells), and damage to vital organs, can be fatal within hours of symptom onset if untreated. Until recently, treatment in Africa relied on chloroquine and sulfadoxine–pyrimethamine. Unfortunately, parasites resistant to both these antimalarial drugs is now widespread. Consequently, the World Health Organization currently recommends artemisinin combination therapy for the treatment of P. falciparum malaria in Africa and other places where drug-resistant malaria is common. In this therapy, artemisinin derivatives (new fast-acting antimalarial agents) are used in combination with another antimalarial to reduce the chances of P. falciparum becoming resistant to either drug.
Why Was This Study Done?

P. falciparum becomes resistant to antimalarial drugs by acquiring “resistance mutations,” genetic changes that prevent these drugs from killing the parasite. A mutation in the gene encoding a protein called the chloroquine resistance transporter causes resistance to chloroquine, a specific group of mutations in the dihydrofolate reductase gene causes resistance to pyrimethamine, and several mutations in dhps, the gene that encodes dihydropteroate synthase, are associated with resistance to sulfadoxine. Scientists have discovered that the mutations causing chloroquine and pyrimethamine resistance originated in Asia and spread into Africa (probably multiple times) in the late 1970s and mid-1980s, respectively. These Asian-derived mutations are now common throughout Africa and, consequently, it is not possible to determine how they spread across the continent. Information of this sort would, however, help experts design effective measures to control the spread of drug-resistant P. falciparum. Because the mutations in dhps that cause sulfadoxine resistance only began to emerge in the mid-1990s, they haven't spread evenly across Africa yet. In this study, therefore, the researchers use genetic methods to characterize the geographical origins and contemporary distribution of dhps resistance mutations in Africa.
What Did the Researchers Do and Find?

The researchers analyzed dhps mutations in P. falciparum DNA from blood samples collected from patients with malaria in various African countries and searched the scientific literature for other similar studies. Together, these data show that five major variant dhps sequences (three of which contain mutations that confer various degrees of resistance to sulphadoxine in laboratory tests) are currently present in Africa, each with a unique geographical distribution. In particular, the data show that P. falciparum parasites in east and west Africa carry different resistance mutations. Next, the researchers looked for microsatellite variants in the DNA flanking the dhps gene. Microsatellites are DNA regions that contain short, repeated sequences of nucleotides. Because the number of repeats can vary and because microsatellites are inherited together with nearby genes, the ancestry of various resistance mutations can be worked out by examining the microsatellites flanking different mutant dhps genes. This analysis revealed five regional clusters in which the same resistance lineage was present at all the sites examined within the region and also showed that the resistance mutations in east and west Africa have a different ancestry.
What Do These Findings Mean?

These findings show that sulfadoxine-resistant P. falciparum has recently emerged independently at multiple sites in Africa and that the molecular basis for sulfadoxine resistance is different in east and west Africa. This latter result may have clinical implications because it suggests that the effectiveness of sulfadoxine as an antimalarial drug may vary across the continent. Finally, although many more samples need to be analyzed to build a complete picture of the spread of antimalarial resistance across Africa, these findings suggest that economic and transport infrastructures may have played a role in governing recent parasite dispersal across this continent by affecting human migration. Thus, coordinated malaria control campaigns across socioeconomically linked areas in Africa may reduce the African malaria burden more effectively than campaigns that are confined to national territories.




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